Posted
by
Soulskillon Saturday July 25, 2009 @05:13AM
from the decompress-the-shuttlebay dept.

sciencehabit writes "A eucalyptus-like tree from New Zealand is still waging a battle that should have ended over 500 years ago. The tree continues to sport evolutionary adaptations, such as barbed leaves, to protect it from a large, flightless bird known as a moa. There's just one problem: the moa went extinct around 1500 AD."

If the leaves don't hurt the tree in its current environment, there's nothing that would keep trees with that particular trait from proliferating, even if the moa is no longer around to weed out the ones without the trait.

Unless it's a disadvantage for the tree to have barbs there is no "reason" for it to change. Evolution is about survival, it is not about changing because something you have is no longer used. I cite our toenails as examples.... do we need them? No. Are they disadvantageous to have for our survival? No. Hence we still have them, even though a significant number of our modern population can no longer see then over their fat guts.

See "The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms" by Connie Barlow. For instance, Osage Oranges were eaten by extinct North American megafauna. In fact, the tree is rather similar to the one in this article, in that it also has sharp spines to defend it.

So here's the thing: We have 46 chromosomes. Our nearest great ape relatives have 48. On the surface, it looks like we must have lost two. But that's actually a huge problem. Made up of organized packs of DNA and proteins, chromosomes don't just up and vanish. In fact, it's doubtful any primate could survive a mutation that simply deleted a pair of chromosomes. That's because chromosomes are to the human body what instruction sheets are to inexpensive, flat-pack furniture. If you're missing one screw, you can still put that bookcase together pretty easily. But if the how-to guide suddenly jumps from page 1 (take plywood panels out of box) to page 5 (enjoy bookcase!), you're likely to end up missing something pretty vital. All this left scientists with a thorny dilemma: How could we have a common ancestor with great apes, but fewer chromosomes?

Turns out: The chromosomes aren't missing at all.
Genetic investigators caught the first sign of the missing chromosomes' scent in 1982. That year, a paper published in the Journal Science described a very funny phenomenon. Researchers knew all chromosomes had distinctive signatures; patterns of DNA sequences that can be reliably found in specific spots, including in the center and on the ends. These end-cap sequences are called telomeres. Telomeres are like the little plastic tips that keep your shoelaces from unravelling. They protect the ends of chromosomes and hold things together. Given that important function, you wouldn't expect to find telomeres hanging out on other parts of the chromosome. But that's exactly what the 1982 study reported. Looking at human chromosome 2, the scientists found telomeres snuggled up against the centromere (the central sequence). What's more, these out-of-place human telomeres were strikingly similar to telomeres that can be found, in their proper location, on two great ape chromosomes.

This evidence laid the groundwork for a brilliant discovery. Rather than falling apart, the two missing chromosomes had fused together. Their format changed, but they didn't lose any information, so the mutation wasn't deadly. Instead, scientists now think, the fusion made it difficult for our ancestors to mate with the ancestors of chimpanzees, leading our two species to strike out alone. In the two decades since the original study, more evidence has surfaced backing this up, which leads us to 2005, when the chimpanzee genome was sequenced around the same time that the National Human Genome Research Institute published a detailed survey of human chromosome 2. We can now see extra centromeres in chromosome 2 and trace how its genes neatly line up with those on chimpanzee chromosomes 12 and 13. It's a great example of evidence supporting the common descent of man and ape.

It's indeed not falsifiable, as someone will just answer "That's because god made it that way!!!!1" to whatever evidence for anything else anyone might present.

Personally, I believe in intelligent design by evolution, and I don't think intelligent design and evolution are exclusive. Instead of angering me, it fascinates me that some people actually try to find evidence that we exist for, what, 6000 years? Creationists are funny people.

Not that this would be a good idea. Greed is a desire to further one's own position. We owe much of our lifestyle to it; capitalism has transformed it into a powerful force for progress. Remove it from society and society will stagnate. It's only a bad thing if it starts trampling on others' rights.

I'm similarly against removing any "undesirable" traits. Who gets to decide what is "desirable"? The traits people view as "proper" tend to be social norms, and do change over time. What gives that person the right to impose his own view of morality on everyone, before they even acquire the capacity to choose their own morality for themselves? What would happen to our individuality?

the change itself has no cost, sure, but it's not that there's a cost to evolve.. evolution is just the result of the pressure of survival and reproduction. there's nothing on the island selecting AGAINST jagged leaves, or at least any pressure on jagged-leaves trees is not strong enough to allow mutant varieties to out-compete the jagged-leaves.

If, in the time that there have been no Moa to eat the plant, no genetic mutation has spontaniously developed that results in no thorns, then why would we expect these trees to have lost stopped growing thorns? Thorns are only expensive if some of your peers are not growing them and you are.

Since these thorns appear to be a defining characteristic of this plants phenotype, and there has only been a small amount of time in which to evolve away from this phenotype (evolutionary time scales are a lot larger than 500 years), it's stupid to assume that they would have dissapeared by now.

Evolution has no plan, it has no engineers deciding what the best design is now that the Moa are dead, it is the net effect of environmental selective pressures combined with the accumulation of small genetic point mutations over time that make one genetic line more likely to reproduce more prolifically, crossed with a whole lot of random chance.